"This is something that Ecuador has been inviting the Swedish prosecutors to do ever since we granted asylum to Mr Assange in 2012.

"There was no need for the Swedish authorities to delay for over 1,000 days before agreeing to carry out this interview, given that the Swedish authorities regularly question people in Britain and received permission to do so on more than 40 occasions in recent years.

"Ecuador has never sought to stand in the way of any legal process in Sweden.

"What we have asked from Sweden, and the UK, are guarantees that Mr Assange will not be extradited to a third country, where he could be persecuted for his work as as a journalist.

"The Ecuadorian government granted asylum to Mr Assange in 2012 given the risk of such political persecution and we believe that this threat remains very real."

The Swedish assistant prosecutor, chief prosecutor Ingrid Isgren, and a Swedish police investigator will be present at the interview and have said that providing Mr Assange gives his consent, a DNA sample will also be taken.

The results of the interview will be reported from Ecuador to the Swedish prosecutors in a written statement. After this report, the prosecutors will take a view on the continuation of the investigation.

Ingrid Isgren will not give interviews during her stay in London, it was made clear.

"As the investigation is ongoing, it is subject to confidentiality. This confidentiality also applies according to Ecuadorian legislation for the investigative measures conducted at the embassy.

"Therefore, the prosecutors cannot provide information concerning details of the investigation after the interview," said a statement.

"I welcome the fact that the investigation can now move forward via an interview with the suspect," said director of prosecution Marianne Ny, who is responsible for the investigation.